...but the corrosion issue for the wing spars is of great concern. Is it possible to check this area out before buying the aircraft?...
The corrosion issue is something that you will have to decide on your own by reading all sides of the issue and then factoring in your best estimate of how credible and/or relevant the various points are to a particular plane. Even the issue of inspection has drawn strong pros and cons. Perhaps this issue is better put as, "is it practical to check out this area to YOUR satisfaction?"
FWIW, I just finished stripping my wing attach fittings down to bare metal in the process of repainting my airplane after 24 years and 1900+ hours of service. I KNOW that my fittings are 100.000% corrosion free on their exterior. I KNOW that there is no sign of debonding, distresss, etc. at the point where the fittings enter the fuselage. I do NOT KNOW anything about the condition of the fittings inside the fuselage except that, given the external condition of the fittings and the overall condition of all other mechanical components of the plane, I would JUDGE the probability of unseen, extensive corrosion of the fittings to be vanishingly small. I am sufficiently comfortable in this judgement to put my butt and my family's souls in the plane. Others would not be satisfied short of sectioning the fittings at quarter inch intervals with a skill saw, and they might still fret that they missed something. These same pilots might (but probably wouldn't?) be comfortable doing low level aerobatics. So it's an exercise in personal judgement and risk analysis which ultimately boils down to "what do I judge to be an acceptable level of risk" - a very personal decision that only YOU can make.
Are there any other problems with this aircraft?...
Like every airplane, the VariEze was designed to excel for a particular mission profile - long range, economical, etc., you know the drill. The farther out of it's 'design box' you try to operate, the closer you are to "problems".
For the Vari-eze drivers out there, how do you like your aircraft?...
I can't imagine selling it. I love it because it fits more of MY "flight missions" (note I didn't say all) better than any other plane. But that doesn't mean it will come close to fitting what YOU want or need in a plane. I'd suggest first deciding on how you would use an 'ideal plane' and then figure out what plane best fits that role (and meets other obvious constraints, like cost). If it's a VariEze, great. If it's a Great Lakes or a Kitfox or a T-18, also great.